An oil cooler is disposed with an upper tube plate and a lower tube plate, each overlapped and welded thereto, to form one plated tube. Generally five to six plated tubes are layered to constitute an oil cooler.
An uppermost plated tube forming an oil cooler is disposed at both distal ends thereof with a pair of nipples for circulating oil. The upper tube plate and the lower tube plate, for forming each plated tube, are respectively mounted with oil holes for communicating with the nipples. Embossed parts are respectively formed at a central area of a plane near the oil holes. The embossed parts function to connect an upper tube plate and a lower tube plate and are coupled by braze welding. Furthermore, the embossed parts also serve to prevent a detachment of assembling positions when inner cooling pins are assembled and also serve to maintain a rigidity of plated tubes at an area where there are no inner cooling pins.